RSSI means Receiver Signal Strength Indicator. It's the strength of the signal as perceived as received by the client. It does not have a precise unit of measurement. On client softwares, it's usually a percentage (that has no real meaning). WLC and APs usually show in dbm.

SNR is Signal/Noise ratio. The noise level is usually at -90dbm let's say. This means that if you have a signal at -90dbm, it's completely lost in the noise, it has a SNR of 0.

A signal at -80dbm has a SNR of 10 in the same conditions, it is barely decodable.

However if the noise level is -95 then a signal of -80 will give a SNR of 15 and will be much more decodable.

Noise is usually between -100 and -90 in normal circumstances.

Dbm is another way of expressing power (rather than milliwatts). The advantage of dbm is that you can add or substract antenna gains very easily since those are in db.

20dbm=100mw

The rule is "if you substract 3dbm, divide the mw by 2" and "if you substract 10dbm, divide the milliwats by 10"

So 17dbm = 50mw

13dbm=25mw

10dbm=10mw

The received signal strength which are usually between -40 and -80dbm are then fractions of fractions of microwatts :-)

In summary, for voice, it's recommended that the "worst" RSSI a phone gets is -67dbm. At that signal level it should be able to roam to an AP having better signal. The coverage cells of APs should also overlap by 20%.

I can see you are working with WCS - how do you recommend to categorize Rogue APs with attributes I have written above (IE RSSI -83, SNR 2, etc.) Because from I have catched, this AP is no harm form my infrastructure.

Personally I dont know that (I) would change anything. Only because if you were to have a rogue on the inside powered very very low you could still reg a -85. I would recommend rogue on the wired implementation.

If any of this is helpful please support the rating system. Its a way for others that use 'search' to find their answers quicker. And well frankly, helps me catch up with Leo ! LOL